use strict;
use warnings;
use Scalar::Util 'looks_like_number';

my @result;
open my $file, "<", "my_big_file" or die "Can't open my_big_file: $!";

while (<$file>)
{
  my @data = split "\t", $_;
  for my $col (0..$#data)
  {
    my $len = $length($data[$col]);
    if (!looks_like_a_number($data[$col]))
    {
      $result[$col]{is_a_string} = 1;
    }
    $result[$col]{max_len} = $len if ($len > $result[$col]{max_len});

    next if $result[$col]{is_a_string}; # Don't check number range if this is a string
  
    # Check number range here
    ...

    # Other stuff
    ...
  }
}